Cooling means for centrifugal clutch unit



Nov. 1, 1955 E. c. KIEKHAEFER 2,722,304

COOLING MEANS FOR CENTRIFUGAL CLUTCH UNIT ZZ g Z5 Filed Aug. 4, 1952 4/zer 22 1 222 2!" Z AMM United States Patent f" COOLING MEANS FORCENTRIFUGAL CLUTCH UNIT Elmer C. Kiekhaefer, Cedarburg, Wis. ApplicationAugust 4,1952, Serial No. 302,481

2 Claims. (Cl. 192113).

This'invention relates to centrifugally operated friction. clutches andparticularly to the engagement of the friction members andcoolingthereof.

The invention provides a series of friction shoes which are allowedlimited axial movement by the end support ing means whereby limitedshaft misalignment is accommodated by movement of the shoes relative tothe retaining. means.

The-invention further provides an air circulating system around thefriction membersto cool the latter and the outside of the clutch unit toincrease the-capacity of the clutch.

An object of the'invention is to allow thefriction shoes tov moverelative to the driven member without effecting the drivingengagement ofthe clutch.

Another object is toprovide an improved centrifugallyoperated clutch oflarger capacity within limited dimensions.

Another object-is to provide a centrifugally operated clutch.whichoperates without noise and vibrationbelow the:predetermined speedfor clutch engagement.

Another object is to provide for the circulation of air around thefrictionareas andthe friction surfaces at all speeds ofoperationincluding speeds belowthat for which. precludes airbornemoisture and foreign particles from theclutch while allowing.adequate'access of air to the clutch members necessary for coolingthesarne:

These and other objects-and advantages will appear in connection withthe following description of vi an" er'n-' bodiment of the inventionillustrated in the accompany-' ing drawings:

In the drawings:

Fig. 1 is a transverse axial section taken through the clutch housingand clutch'unit;

Fig. 2 is an'end elevation of the"driven clutch element with the clutchbroken awayand sectioned-to show the friction shoes and retainingspring;

Fig. 3 is a side elevation of the drive clutch. means shown in Fig. 1with several of the frictionsh'oes removed .to show the retainingspringand end members; and

Fig. 4 is a transverse section showing the location of the supplementaryair entry ports for cooling. the friction shoes.

The clutch unit 1 shown in the drawings is particuany adapted for chainsaws such as that shown 'and described in thecopendingapplication'of theinventor entitled Transmission Unit for Chain Saws, Serial No. 301,702,filed July 30, 1952.

The clutch housing 2 comprises the cylindrical outer member 3 formedintegrally with the crank case 4 of the chain saw engine and the covermember 5 secured 2,722,304 Patented Nov. 1 .1955

ice

2i to the periphery of member 3' and formed integrally; with thetransmission case 6. I I

TheprOjectingQend of drive shaft 7 which'extends intohousing.,2"is-supported by the bearing-8 in :crank case 4. The drivenshaft 9 supported by. the bearing. 10 is carried by: transmission case 6and extends there-- from into housing 2 in end to-end relation: withshaft 7. The-driveclutch element 11 is rotationally secured on the endof shaft 7 b y, the key-IZ- and fixed thereonby. the bolt assembly13'w-ithinhousing-12 The drivenclutch element comprises the drum t whichis closed at-one end 16ithereofan d which is fixed on the splined end ofshaft 9 by the-bolt 14.] I

The interlocking annular fianges- 17 and =18 of-member 3 and cover 5,respectively are adapted to: be secured by, the ringclampl9 andnormally, secure transmission case'6-to crank case 4' ofthechaimsawunit-- Loosening or removal of the ring clamp 19 allows-cover 5 andtransmissioncase- 6 to b eadjusted-rotationally: relative to member 3andcrank case 4-respecting-theraxis of shafts-7 'and 9" for variousconditions of chain" saw operation.- Removal: of ring clamp 19 while theclutch is not beingdri-ven allows drum '15 tobewithdrawn from housing 2andthe transmission case-G to-be detached 'from crank case 4 as'desired,-.suchasfor the 1 separate transportingof the respectivepartsof-the -chain saw unit. I p I 7 I Tli'e drivingclfitch element 11includes the; flanged hub 20" mounted directly on shaft 7 and thecircular plates 21 securedby. the bolts 22 to theopposite'sides of hub20. Each-plate is formed'with a series ofradial slots- 23 which openoutwardly-of the periphery of each plate- The ribs 24 between adjacentslots extend-radiallyfromthe rim 25 of each plate 21 closing v theinnerend of theslots ZKof the plate. Each rim 25 is fiared in w'a'rdly,forsecurement-b'y the bolts 22 to the-hub 20-asdescribed". and isoppositely offset to space slots 23 axially respecting, shaft 9 andtoreceive the friction shoes 25; i I

Each shoe 26 comprises a block of suitable rnateriah of generally,rectangular outline and of wedge-shaped: cross-sectiongenerally,correspondinguto thearea of slots 23. formed byrim 25- and theradially. extendi ng-ribs-- 24.- Each sh'oe or block 26 is provided witha transverseopening 27 between-the endsthereof-to receive the-spring:-28? Spring 28 extends circularly about the axisofshaft-l through theopenings 27' of b1ocks26 as arranged radial ly.and supportedat oppositeends within slots-23.

Atf idling, speeds; spring 28 is tensionedto secure blocks 26 radially.inwardly andseatthe ends-"thereof racliall'y inwardly against therim 25of each-plate=-21.== At'h'igher speeds ofsh aft- 7 spring-.=28expandsradially allowingblocks 26 to move radiallyoutwardlyby cen-tritugalforce andinto engagement 'with the inner faceofdr-u'm' 15. At suchhigher speeds, centrifugalforce;- measured-by the angular velocity ofspring '28 -and-blocks- 27, maintains the blocks in frictionalcontactwith drum 15fto-drive-th'e latter and effect the rotation of drivenshaft 9." The-torque etfecting rotationaof driven s ha ft -9'is'transmitted from shaft Tthrough ribs 24 against-the ends of blocks26.

In the operation of the cl'iitch unitthe angular mis alignment 'ofshafts 7 and'9causes relative axial move= ment between drum'15;andthedrivingclutch element-- ll with eachrotation thereof. Such misalignment-is unavoidable in actual service where the parts are separated anddismantled frequently and careful reassembly cannot be depended on.

According to the invention, a substantial clearance between the ends ofthe shoe blocks 26 and plates 21 is provided whereby limited axialmovement of each block respecting plates 21 is permitted.

The clearance provided allows the blocks to move axially relatively tothe plates and to remain in frictional engagement with the inner face ofdrum whereby the engaging faces of the blocks and drum 15 are securedagainst frictional wear.

The invention additionally provides for the air-cooling of the blocksand drum interior by controlled recirculation of the air within thehousing and the cooling of the drum exterior from the outside Withoutallowing entry of dust and foreign particles to the housing.

In the driving clutch element 11, the milled cutaway portions 31 provideopenings through rims radially inwardly of the blocks 26 and normallyprovide clearance for the heads 29 and nuts 30 of bolts 22 by theadditional openings 32, provided in the end 16 of drum 15. The milledcutaway portions 31 and openings 33 in plates 32 between bolts 22provide for the circulation of air through the drum with rotation ofclutch element 11 and blocks 26. During operation of the clutch orrotation of clutch element 11, element 11 acts as a fan which drives theair within drum 15 for discharge axially outwardly from the outer openend of the drum. Openings 32 and 33 in rims 25 of plates 21 and openings32 in drum 15 provide for the admission of air to the blocks 26 betweenplates 21 to cool the blocks. The air passes by centrifugal force overthe blocks radially outwardly against the inner face of drum 15 to carrysmall particles worn from the friction face of the blocks and removethem from the interior of the drum. The air discharged from theperiphery of the drum passes between plate 21 adjacent to the end ofcrank case 4 and moves radially inwardly within housing 2. The series offlanges 34 may be provided within housing 2 at the end of crankcase 4 toextend radially of shaft 7 and to retard the rotational velocity of theair as it reaches the drum and effect thereby the greater circulation ofthe air inwardly toward openings 31 and 33.

The annular series of grooves formed in the outer periphery of drum 15provide a series of fins 35 for the increased exposed cooling area ofthe outside of the drum. The openings 36 in housing member 3 adjacent tofins 35 and between the ends of drum 15 allow for the admission orexhaustion of limited amounts of air to or from within the housing withthe expansion or contraction of the air therein and provide a constantcirculation of air between fins 35 of the drum. A minimum operatingclearance is provided between the outer dimension of fins 35 and theinterior of housing member 3 whereby fins 35 serve to preclude the entryof foreign particles, such as dust and dirt entering housing 2 throughopenings 36 from reaching either end of housing 2 and the interiorthereof and whereby the dependable operation of the clutch unit underconditions normally encountered in chain saw operation is provided.Normal breathing of the housing with contraction and expansion of theair therein is allowed without admission of foreign particles thereto.Limited exposure of drum 15 through openings 27 to the outside air isalso provided thereby. With each rotation of drum 15 a certain amount ofair between flanges 34 is expelled through openings 36 and is replacedby outside air which enters through the same or other openings and iscarried about the interior of housing 3 to cool the latter and betweenfins 35 to cool the drum. v

The desired maximum capacity of the clutch unit of limited size isprovided by the adequate cooling of the clutch. The relative movement ofthe friction blocks provided for, increases the serviceability of theclutch unit and reduces the actual cooling requirements of the clutch.

Various embodiments of the invention may be employed Withinthe scope ofthe following claims.

I claim:

1. In a centrifugally operated clutch transmission unit for chain sawsand the like, a cylindrical housing having an end wall, a drive shaftrotatably supported by said end wall and projecting centrally into saidhousing, a drum rotatably supported within said housing andconcentrically of said drive shaft, a series of friction blocks radiallyarranged within said drum and adapted to engage the latter, and a drivemember fixed to said drive shaft within said drum and having radial ribssupporting said blocks to rotate the same and effect the rotation of thedrum, said drive member having openings adjacent said end wall wherebythe rotation of said drive member effects the circulation of air throughthe interior of the drum and between said end wall and said drive memberfor transfer of heat to said end wall, a series of annular finsextending about said drum and formed integrally therewith and having anouter dimension sutficient to provide a minimum operating clearance withthe interior of said housing, and a series of openings in said housingexposing portions of said drum and said fins for the circulation of airtherethrough and between said fins to cool the exterior of said drumseparately of the circulation of cooling air through the interiorthereof and to provide for the cooling of said end wall by the transferof heat therefrom to the housing cooled by the rotation of the drum.

2. In a centrifugally operated clutch transmission unit for chain sawsand the like, a cylindrical housing having opposite end walls, drive anddriven shafts rotatably supported in approximate alignment within saidhousing and in end-to-end relation, a drum having a supporting end fixedto said driven shaft and a series of annular fins extending about saiddrum and formed integrally therewith and having an outer dimensionsufiicient to provide a minimum operating clearance with the intesame, aseries of friction blocks radially arranged within said drum and adaptedto engage the latter, and a drive member fixed to said drive shaftwithin said drum and having radial ribs supporting said blocks to rotatethe same and effect the rotation of the drum, said drive member and drumhaving openings adjacent the corresponding end walls of said housing anddisposed radially inwardly of said blocks for the circulation of airthrough the interior of the drum and in heat exchange relation with thecorresponding end walls, and a series of openings in said housingexposing portions of said drum and said fins for the circulation of airtherethrough and between said fins to cool the exterior of said drumseparately of the circulation of cooling air through the inte riorthereof and to provide for the cooling of said end walls by the transferof heat therefrom to the cylindrical housing cooled by the rotation ofthe drum.

References Cited in the file of this patent UNITED STATES PATENTS1,866,291 Bryson July 5, 1932 1,971,929 Burdick Aug. 28, 1934 2,000,713Norris May 7, 1935 2,487,936 McCrady et al Nov. 15, 1949 2,504,177Bruestle Apr. 18, 1950 FOREIGN PATENTS 64,274 Sweden Dec. 13, 1926240,449 Great Britain Sept. 18, 1925 303,149 Great Britain Feb. 21, 1930470,912 Great Britain Aug. 24, 1933 828,455 France Feb. 14, 1938

